Glass composition



United States Patent GLASS COMPOSITION William W. Welsch, Granville, Ohio, assignor to Owens- Corning Fiberglas Corporation, a corporation of Delaware No Drawing. Application June 20, 1955 Serial No. 516,785

8 Claims. (Cl. 106-50) This invention relates to a glass composition which is especially adapted for the manufacture of glass articles such as fibrous glass and the like.

Fibers have been produced in the past by various methods from glass, slag, fusible rock, and various other materials. Commercial manufacture of fibers from molten glass has been accomplished by subjecting the softened material to high velocity gaseous blasts which attenuate the material to fibers. Stem, compressed air, and hot exhaust gases from a combustion burner have been used as attenuating forces in the known process. Recent processes utilize centrifugal forces for delivering bodies of glass into an annularly shaped gaseous blast which attenuates the glass into very fine fibers having high quality and greatly improved physical properties. For a description of one such process, see US. Patent 2,609,566, Slayter and Stalego.

The glass composition to be used with such a process must have particular physical properties which make it possible to use the glass in the process. The rotary process referred to comprises delivering into a rotor or spinner operating at high speed the material which has been heat-softened. The material is then directed outwardly through openings in the periphery of the spinner as individual bodies which are delivered generally radial- 1y of the spinner into the annular blast from a burner. The glass compositions of this invention are melted by conventional practices known to the art and require no special treatment during melting or fining.

It is an object of this invention to provide a glass composition having a low liquidus temperature, a wide range of temperatures at which the glass can be attenuated, and a slow rate of devitrification.

It is also an object to provide an improved glass composition especially adapted for use with a rotary process for producing fibrous glass.

It has been discovered that a glass comprising silica and the usual glass-forming ingredients plus an addition of boric oxide and a compound containing fluorine provides the physical properties which are desired for producing fibrous glass by a rotary process. The glass compositions of. this invention may be utilized in other fiber-forming processes in which it is desirable to have a wide range of fiber-forming or attenuating temperatures.

A suitable glass composition comprises the following ingredients expressed in weight percent:

Ingredients: Proportion SD: 50 to A1303 Oto 8 CaO o to 10 MgO Oto 10 t Alkali (Na- O and K 0) 10 to 20 B 0; 3 to 10 CaF, 5 to 15 TiO, Oto 8 Oto 8 "ice 2 Apreferred range of proportions for the various ingradients in the glass compositions is as follows:

Ingredients: Proportion SD: 52 to 63 A1203 2) 6 CaO lto 9 MgO 1 to 9 Alkali (Na o and K 0) 12 to 18 B 0 4m 9 CaF 6 to 14 TiO 2to 6 ZrO 2to 6 The following examples are compositions which have been prepared and used in fiber forming processes.

The liquidus temperature of this glass is 1755 F. and the temperature at 1000 poises is 1880 F.

Example 2 Ingredients: Proportion SiO; 5 8.2 A1 0 3.0 CaO 1.6 MgO 1.2 N2 0 and K 0 16.2 2 3 6.0 caF, 9.0 ZrO 4.8

The liquidus temperature of this glass is 1650 F., the softening point is 1283 F. and the temperature at a viscosity of 1000 poises is 1885 F.

Example 3 Ingredients: Proportion SiO 61.4 A1 0 3.0

CaO 3.3 MgO 2.4 N320 and K20 2 3 6.1 CaF 9.2

The liquidus temperature of this glass is 1730 F. and the temperature at 1000 poises is 1835 F.

Example 4 Ingredients: Proportion SiO 53.5 A1 0 3.0 CaO 5.4 MgO 3.9 Na O and K 0 14.4 B 0 6.0 CaF 9.0 ZrO 4.8

The liquidus temperature of this glass is 1715 F. and the temperature at 1000 poises is 1790 F.

i g a s s pcsi iqn hasb e f und to be pe y pt d o t e r tary p ocess... s liqu dus temp ra s 1 ,653., e. s tening. point bo t. 77' e mp ea a v ccsi ypf. DO.P .i es ..is.175 nd ed sity is 2.64,

het oye asss mnq itiaasptoyi e.a liqu usi pe ature .i qmma outrl' flof a pllttl ofi? This relatively low liquidus makes it possible to run the glass compositions through glass handling apparatus at --re1a tively low. temperatures. which preserve the life'of the glass handling equipment. Theseglasses have a slow rate of crystal formation and growth. The viscosity of these glasses is lower than the conventional glass compositions used formerly in processes utilizingsteam asthe attenuating force The durability of. theseglasses is good and it has been foundthat thedurability can be improved by adding certain inorganic salts such as aluminum salts to theresinous. binders used on thefibers.

It is believed that. fluorine is anessential ingredient in the composititons., Fluorine assists in melting, reduces viscosity, reduces liquidus, ,and improves durability. It hasv been found thatthese glasses can. be. readily melted and fined in large quantities in continuous tanks at glass temperatures offrom,2 30 0 to'2350 -F; Fluorine lowers the viscosity and, in addition, it has been found that fluorine lowers the liquidus in. these compositions by as much asZOO" to 300 F. The simultaneous lowering ofv viscosity and liquidus was an unexpected result and afeature which makes this glass especially adapted for fiber, forming. In prior work fluorine has had no effect on the liquidus of the glass compositions tried. Fluorinealso improves glass durability due to'its acidic nature. Fluorine maybe added in various forms; however, it has been found that fiuorspartCaF is preferred since it is readily available and for-this reason less expensive.

Boric oxide is an essential ingredient and serves a dual function.- The boric oxide provides chemical .durability in the glass and decreases thewiscosity .of the glass composition.

Calcium oxide and magnesium oxide are added to the glass composition in order t0lower the viscosity and increase the fluidity. Calcia and magnesia ordinarily cannot be tolerated in low liquidus glass compositions; however, the above compositions, even though low liquidus glasses, are improved by the addition ofthesc ingredients. The calcia and magnesia are not essential ingredients but they are preferably added toprovide low viscosity.-

Titania and zirconia may be used to improve thedurability, to lower the liquidus and viscosity, and to lower thedevitrification rate. Titania and zirconia are relatively expensive ingredientsand maybe omitted if a low cost glass is necessary.

Alumina is not an essential ingredient but it does assist invmaintaining durability. It may be replaced partially or fully by silica.

Barium oxide may beusedtolower the liquidus; howve t use of b at ntlslq i 9! seth de y o e glass and may be undesirable for this reason,

Soda is used'as a flux to assist in melting and to lower the viscosity and liquidus. It should not be used in excess since loss of durability will result.

The examples given above are starting or theoretical compositions and the actual glass compositions resulting from melting thesecbateh ingredients may be somewhat difierent due to; the-.. high ,losses of,.volatilesjncluding;

. 4.; fluorine, B 0 and Na O. Some fluorine is probably retained in-the glass formed, however; and it is believed its presence provides some of the properties desired.

The above glass compositions are especially adapted for use in the rotary process where the spinner is preferably operated at a relatiyely low temperature to reduce the erosion and oxidation-of 'the spinner during use. Low operating temperaturesare ,made; possible by the glass compositions disclosed with the result that the spinnerand other glass handlingapparatus have a greater useful life. High-fluidity atthe-liquidus temperature and at the operating temperature is provided by these compositions.

Various modificati9ns and,,variations may be made in the present invention within the spirit and scope of the appended claims.

I claim:

1. A glass batch consisting essentially by weight:

e s nt SiO 4 52 to 63 1203.-

m, '6 Cat) ,7 U 9 Q. t0.,, azQ n Kzq -r. 1 w 205. 9 z r t. r. 14 Qzf v. a O 6 ZrQ; 2w 6 2. :A "glass tbatch comprisingr.by'sweight:

Percent SiO 57.2 A1 0 3.0 CaO 5.5 MgO 4.0 Na O and K 0 14.8 B 0 1 6.2 CaFg- 9.3

3. A glassbatch comprising by weight:

Percent SiO 53.5 A1 0 3.0 0:10" 5.4 MgO 3.9 Na O and K 0 14.4 B 0 6.0 caFzi 9.0 ZrO C 4.8

4. A.v glassbatchcomprising '-by weight:

Percent SiO 61.4 A1 0 3.0 CaO 3.3 Mg0 W 2.4 Na O and K 0 14.6 B 0 6.1 CaF, 9.2

5. A glass batch'comprising by weight:

Percent SiO; 7 58.2 A1 0,, 3.0 0210' i 1.6 MgO 1.2 Nazo'and B 0 6.0 03F: 9.0 Z20 4.8

.5 6. A glass batch comprising by weight:

Percent SiO, 56.6 10,0, 2.9 CaO 1.6 M20 1 1.1 Na 0 and K 14.0 B 0, 5.9 CaF, 8.8 no, 4.5 ZrO, 4.6

7. As an article of manufacture fibrous glass produced from the following batch:

Percent by weight SiO 57.2 A1 0, 3.0 CaO 5.5 MgO 4.0 Na o and K 0 14.8 13,0, 6.2 CaF, 9.3

8. A glass batch consisting essentially by weight:

Percent SiO, 7 53.5-61.4 A1 0 2.9- 3.0 CaO 1.6- 5.5 MgO 1.1- 3.9 Na O and K 0 14.0-16.2 B 0 5.9- 6.2 CaF 8.8- 9.3 TiO;, 0- 4.5 ZrO: 0 4.8

References Cited in the file of this patent UNITED STATES PATENTS 2,426,472 Stanworth Aug. 26, 1947 2,429,432 Stanworth Oct. 21, 1947 2,687,968 Beck Aug. 31, 1954 FOREIGN PATENTS 897,060 France Mar. 12, 1945 905,421 Germany 1954 OTHER REFERENCES Locke: The Glass Industry, vol. 7, No. 6 (1926),

page 136. 

7. AS AN ARTICLE OF MANUFACTURE FIBROUS GLASS PRODUCED FROM THE FOLLOWING BATCH: 100.0 